I would like to remind you guys, that steam engines or light(wood) gas engines are quite good for situations where you have no traditional fuel aviable. Both russians and germans used such devices, and my grandpa used to drive one in siberia. When he run out of fuel he just stopped and cut down some trees, and he was ready to go!:D

You still have the weight of the fuel to worry about, though. A kilo of gas contains about 47 megajoules of energy, a kilo of wood only about 16.

That means that if you had a 20-gallon gas tank, and assuming that you had a steam engine that can convert wood to energy at the same rate an internal combustion engine (Which is a looooooong stretch), you would need about 160 kilograms of wood. That's about what a small tree weighs.

You still have the weight of the fuel to worry about, though. A kilo of gas contains about 47 megajoules of energy, a kilo of wood only about 16.

That means that if you had a 20-gallon gas tank, and assuming that you had a steam engine that can convert wood to energy at the same rate an internal combustion engine (Which is a looooooong stretch), you would need about 160 kilograms of wood. That's about what a small tree weighs.